The present invention relates to instruments for more accurately controlling the placement of implant material thereof, during surgical procedures for the repair of hard tissue by injection of hard tissue implant materials. Procedures for such repair include hip augmentation, mandible augmentation, and particularly vertebroplasty, among others.
Polymethylmethacrylate (PMMA) has been used in anterior and posterior stabilization of the spine for metastatic disease, as described by Sundaresan et al., xe2x80x9cTreatment of neoplastic epidural cord compression by vertebral body resection and stabilization.xe2x80x9d J Neurosurg 1985;63:676-684; Harrington, xe2x80x9cAnterior decompression and stabilization of the spine as a treatment for vertebral collapse and spinal cord compression from metastatic malignancy.xe2x80x9d Clinical Orthodpaedics and Related Research 1988;233:177-197; and Cybulski, xe2x80x9cMethods of surgical stabilization for metastatic disease of the spine.xe2x80x9d Neurosurgery 1989;25:240-252.
Deramond et al., xe2x80x9cPercutaneous vertebroplasty with methyl-methacrylate: technique, method, results [abstract].xe2x80x9d Radiology 1990;117 (suppl):352, among others, have described the percutaneous injection of PMMA into vertebral compression fractures by the transpedicular or paravertebral approach under CT and/or fluoroscopic guidance. Percutaneous vertebroplasty is desirable from the standpoint that it is minimally invasive, compared to the alternative of surgically exposing the hard tissue site to be supplemented with PMMA or other filler.
The general procedure for performing percutaneous vertebroplasty involves the use of a standard 11 gauge Jamshidi needle. The needle includes an 11 gauge cannula with an internal stylet. The cannula and stylet are used in conjunction to pierce the cutaneous layers of a patient above the hard tissue to be supplemented, then to penetrate the hard cortical bone of the vertebra, and finally to traverse into the softer cancellous bone underlying the cortical bone.
A large force must be applied by the user, axially through the Jamshidi needle to drive the stylet through the cortical bone. Once penetration of the cortical bone is achieved, additional downward axial force, but at a reduced magnitude compared to that required to penetrate the cortical bone, is required to position the stylet/tip of the cannula into the required position within the cancellous bone. When positioned in the cancellous bone, the stylet is then removed leaving the cannula in the appropriate position for delivery of a hard tissue implant material to reinforce and solidify the damaged hard tissue.
A syringe is next loaded with polymethyl methacrylate (PMMA) and connected to the end of the cannula that is external of the patient""s body. Pressure is applied to the plunger of the syringe to deliver the PMMA to the site of damaged bone at the distal end of the cannula Because in general, 10 cc syringes are only capable of generating pressures of about 100-150 psi, this places a limitation on the viscosity of the PMMA that can be effectively xe2x80x9cpushed throughxe2x80x9d the syringe and cannula and fully delivered to the implant site. Of course, the use of a small barrel syringe, e.g., a 1 cc syringe, enables the user to generate higher driving pressures. For example, pressures of 1000 psi and possibly as high as 1200-1500 psi (depending upon the strength of the user and the technique) may be generated using a 1 cc syringe. A serious limitation with the use of a 1 cc syringe, however, is that it will not hold a large enough volume to complete the procedure in one step or xe2x80x9cloadxe2x80x9d and must be reloaded several times to complete the procedure, since, on average, about 3.5 cc of implant material per side of the vertebral body are required for an implantation procedure. This makes the procedure more complicated with more steps, and more risky in that the polymerization of the implant material causes it to become increasingly more viscous during the additional time required for reloading. Another problem with a 1 cc syringe is lack of control, as high pressures are generated in a xe2x80x9cspike-likexe2x80x9d response time and are not continuously controllable.
A viscous or paste-like consistency of PMMA is generally believed to be most advantageous for performing percutaneous vertebroplasty. Such a consistency insures that the implant material stays in place much better than a less viscous, more liquid material. Leakage or seepage of PMMA from the vertebral implant site can cause a host of complications some of which can be very serious and even result in death. For example, Weil et al. reported cases of sciatica and difficulty in swallowing which were related to focal cement leakage, Radiology 1996; Vol 199, No. 1, 241-247. A leak toward the distal veins poses an even more serious risk, since this can cause a pulmonary embolism which is often fatal.
In addition to the viscosity effects noted above that require greater pressure to deliver hard implant tissue material, when such material (like PMMA) is implanted percutaneously, the need to inject it through a relatively narrow needle or cannula also greatly increases the need for a high pressure driver. Still further, implantation of PMMA into a relatively closed implantation site (e.g., trabecular bone) further increases the resistance to flow of the PMMA, at the same time increasing the pressure requirements of the driver. Thus, there is a need for a high pressure applicator that has enough storage capacity to perform a complete implantation procedure without having to reload the device in the midst of the procedure, and which is consistently controllable, for an even, constant application of pressure during delivery of the entirety of the implant material.
Attempts have been made to increase the ability to apply pressure to drive PMMA to the vertebral implant site by providing a smaller barrel syringe, but this holds less volume and must be refilled once or several times to deliver enough volume of PMMA to the site. Since there is a limited amount of time to work with PMMA before it begins to polymerize or set up, this type of procedure is more difficult to successfully complete within the allotted time, and thus poses an additional risk to the success of the operation.
Accordingly, there exists a need for an improved apparatus and procedure for controllably applying higher pressures to a source of implant material, and particularly to hard tissue implant materials, to successfully implant the material at the desired location in a single batch, for the performance of vertebroplasty and particularly, percutaneous vertebroplasty.
The present invention includes a high pressure applicator for driving the delivery of a flowable tissue implant material. A first column having an inner wall, an outer wall, a first open end and a second substantially closed end is provided with an orifice through the substantially closed end for passage implant materials therethrough under high pressure. A second column is drivably engageable with the first column to generate fluid pressure within at least the first column. Preferably, a wall portion of the second column is drivably engageable with one of an inner and outer wall of the first column. A handle is preferably fixedly attached or integral with the first column and may extend radially from the first column to provide a user a mechanical advantage upon grasping it.
At least one sealing element may be provided to interface with the inner wall of the first column, to enhance the generation of pressure in the first column. A handle is also preferably integrally formed with or affixed to the second column and may extend radially therefrom to provide a user a mechanical advantage upon grasping it.
In one embodiment of the invention, threading is provided on an outer wall of the first column. The second column is substantially hollow, having an open first end, a closed second end and threading on an inner wall thereof. The threading on the second column in this embodiment is engageable with the threading on the first column to provide a driving force for driving the second column with respect to the first column. The second column may include an extension integrally formed with or affixed thereto and optionally having an end portion extending from the open end of the second column. The extension is adapted to be inserted through the open end of the first column and form a substantial pressure seal with the inner wall of the first column.
Additionally, at least one sealing element may be provided at or near the end portion of the extension to form or enhance a pressure seal with the inner wall of the first column. The sealing element(s) may be an O-ring(s), a grommet(s) or the like.
In another embodiment, a plunger element is provided which is adapted to be inserted within the first and second columns. The plunger element has a first end portion and a second end portion, where the first end portion is adapted and configured to closely fit within the inner wall of the first column to form a pressure seal therewith. At least one sealing element may be provided for the first end portion to form and/or enhance a pressure seal between the inner wall and the plunger element. A handle may be integrally formed with or affixed to the second column, to optionally extend radially therefrom, to provide the user a mechanical advantage upon grasping it. The plunger element may further be provided with at least one frictional element mounted to the second end portion and adapted to form a disengageable friction fit with the second column at or near the closed end of the second column.
A high pressure applicator according to the present invention may include threading on at least a portion of the inner wall of the first column, and the second column may have threading on at least a portion of an external wall thereof such that the threading of the external wall is engageable with the threading on at least a portion of the inner wall of the first column to provide a driving mechanism for driving the second column with respect to the first column. The interengaging threads may be formed to closely fit to form a pressure seal therebetween upon their engagement. At least one sealing element may be mounted to an end portion of the second column and adapted to form or enhance a pressure seal with the inner wall thereby forming or enhancing the pressure seal between the first and second columns. The sealing element(s) may comprise an O-ring(s), a Teflon wrap(s), or the like. A handle may be integrally formed with or affixed to the second column to extend radially therefrom, to provide a user a mechanical advantage upon grasping it.
Various portions of a pressure applicator may be sized to provide sufficient mechanical advantage to enable the application of pressures up to about 3000 or 4000 psi by hand. The mechanical advantage of an applicator is determined in large part by handle size, the bore size of the first column, and the mechanical advantage of the engagement mechanism. With regard to the engaging threads used as an engagement mechanism, manufacturing and material considerations, and the diameter on which to place the threads will determine the thread pitch which may be used. This in turn determines the mechanical advantage of this engagement mechanism. Where a greater mechanical advantage is desired, a finer thread pitch will provide the same. To achieve this, the diameter of threaded sections of the first and second columns may be decreased. Alternately, a finer pitch thread may be used on a relatively larger diameter section by changing material or manufacturing procedure (such as cutting the threads into the respective members rather than molding the pieces as is presently preferred). In all, a pressure applicator produced according to the present invention is a balancing of various design goals relating to performance and cost.
In an arrangement where the threads cover only a portion of the external wall, the remainder of this wall of the second column is left relatively smooth. In this arrangement, only a portion of the inner wall of the first column has threads, and the remainder of the inner wall is left substantially smooth. The relatively smooth end portion of the second column has a reduced diameter section having an outside diameter less than an inside diameter of the threads on said inner wall, to allow assembly or interfitting of the two columns. An enlarged section extending from the reduced diameter portion closely fits with the substantially smooth inner wall to form a pressure seal therewith. The first column in this arrangement additionally includes a hinged or removable section adapted to swing open or be removed therefrom to allow insertion of the second column At least one sealing element, which may be an O-ring or the like, may be mounted to the end portion of the second column to form or enhance a pressure seal therewith.
In yet another embodiment, the first column is substantially hollow and comprises an inside wall, an open first end and a closed second end, and a barrel portion of a syringe is received therein. A plunger portion of the syringe is received within a second column. The applicator may include threading on an outer wall of the first column and threading on an inner wall of the second column, where the threads are engageable with one another to provide a driving force for driving the plunger portion with respect to the barrel portion. A handle may be integrally formed with or affixed to the second column and optionally extend radially therefrom and to provide the user a mechanical advantage upon grasping it.
An end of the barrel portion of the syringe may abut against the substantially closed end of the first column and an end of the plunger portion may abut against the closed end of said second column, such that driving of the second column with respect to the first column provides a driving force for advancing the plunger portion within the barrel portion. The barrel portion may further include a wing or flanged portion adjacent an open end thereof. The first column may have a first portion adjacent the open end, a second portion adjacent the substantially closed end and a transitional portion joining the first and second portions, where the first portion has an inside diameter larger than an inside diameter of the second portion. In this case, the transitional portion may be adapted to abut against the wing or flanged portion, to provide additional or alternative support for the barrel portion as the plunger portion is being advanced with respect thereto.
Alternatively, a high pressure applicator according to the present invention may include a syringe having a barrel portion and a plunger portion, where the syringe barrel is received within the first column where threading is provided on at least a portion of the inner wall of the first column and on at least a portion of an external wall of the second column. In this embodiment of the invention, the second column includes an end adapted to abut an end of the plunger portion of the syringe and threading of the external wall is engageable with the threading on at least a portion of the inner wall to provide a driving force. The operation and variations of this embodiment are substantially like those described directly above.
A method of preparing a high pressure applicator for driving the delivery of a flowable tissue implant material for use is disclosed to include: providing an applicator having a first column having an inner wall, an outer wall, a first open end and a second substantially closed end having an orifice therethrough, and a second column drivably engageable with the first column to generate a pressure within the first column; loading the flowable tissue implant material into the first column; engaging the second column with the first column to enclose the tissue implant material; and advancing the second column toward the first column to generate a pressure for driving the flowable tissue material through the orifice.
The second column may include a plunger adapted to form a pressure seal with the inner wall of the first column, in which case the engagement of the second column with the first column includes introducing the plunger into the tissue implant material in such a way to avoid the introduction of air bubbles or other compliant matter together with the implant material to be delivered to a patient. Advancement of the second column toward the first column generates a pressure for driving the flowable tissue material through the orifice, which may be at least 1000 psi. Optionally, a substantially non-compliant tube may be connected to the orifice prior to advancing the second column toward the first column to generate a pressure for driving the flowable tissue material through the orifice.
As another option, a substantially non-compliant tube may be connected to the orifice after advancing the second column toward the first column to generate a pressure for driving the flowable tissue material through the orifice, thereby purging the orifice prior to connecting the substantially noncompliant tube. In either case, the substantially noncompliant tube may be, but is not necessarily prefilled (e.g., with saline or implant material) prior to connecting it to the orifice.
Loading of the first column with implant material may be done in such a way as to slightly overfill the first column to form a meniscus created by surface tension of the implant material. In this case, the engagement of the first and second columns then may include introducing a plunger element into the implant material and then driving the plunger via the advancement of the second column.
A method of preparing a high pressure applicator for driving the delivery of a flowable tissue implant material for use is provided which includes: providing an applicator containing at least 5 cc of tissue implant material therein; and actuating the applicator to generate an internal pressure of at least 1000 psi which acts as a driving force to force a flow of the implant material from the applicator. The pressure generated may be at least 1500 psi, at least 2000 psi, at least 2500 psi or up to about 3000 psi.
Further, the method is described as torquing a first portion of the applicator with respect to a second portion of the applicator actuator to generate the driving force. The applicator may be provided to contain at least 7.5 cc of tissue implant material, up to 10 cc of tissue implant material, or even up to about 15 cc of tissue implant material therein. A preferred embodiment currently holds about 9 cc of implant material.